Upstart notes for RHEL

Upstart is an event-based init system. Red Hat Enterprise Linux (RHEL) first started using in version 6.

From the RHEL 6 Technical notes.

Upstart

In Red Hat Enterprise Linux 6, init from the sysvinit package has been replaced with Upstart, an event-based init system. This system handles the starting of tasks and services during boot, stopping them during shutdown and supervising them while the system is running. For more information on Upstart itself, refer to the init(8) man page.

Processes are known to Upstart as jobs and are defined by files in the /etc/init directory. Upstart is very well documented via man pages. Command overview is in init(8) and job syntax is described in init(5).

Upstart provides the following behavioral changes in Red Hat Enterprise Linux 6:

• The /etc/inittab file is deprecated, and is now used only for setting up the default runlevel via the initdefault line. Other configuration is done via upstart jobs in the /etc/init directory.
• The number of active tty consoles is now set by the ACTIVE_CONSOLES variable in /etc/sysconfig/init, which is read by the /etc/init/start-ttys.conf job. The default value is ACTIVE_CONSOLES=/dev/tty[1-6], which starts a getty on tty1 through tty6.
• A serial getty is still automatically configured if the serial console is the primary system console. In prior releases, this was done by kudzu, which would edit /etc/inittab. In Red Hat Enterprise Linux 6, configuration of the primary serial console is handled by /etc/init/serial.conf.
• To configure a getty running on a non-default serial console, you must now write an Upstart job instead of editing /etc/inittab. For example, if a getty on ttyS1 is desired, the following job file (/etc/init/serial-ttyS1.conf) would work:

  # This service maintains a getty on /dev/ttyS1.
  
  start on stopped rc RUNLEVEL=[2345]
  stop on starting runlevel [016]
  
  respawn
  exec /sbin/agetty /dev/ttyS1 115200 vt100-nav
  

As in prior releases, you should still make sure that ttyS1 is in /etc/securetty if you wish to allow root logins on this getty.

There are some features from prior releases that are not supported in the move to Upstart. Among these are:

• Custom runlevels 7, 8 and 9. These custom runlevels can no longer be used.
• Using /etc/shutdown.allow for defining who can shut the machine down.

Upstart is taken care of by Canonical at https://launchpad.net/upstart with the home of it at http://upstart.at/.

The Upstart Cookbook has some good information regarding syntax and such.